HomeMy WebLinkAboutUSFS Juneau Ranger & Mendenhall Glacier Visitor Center Biomass GregKoontz 09-24-2014-BIOUSFS
Juneau
Ranger
District
&
Mendenhall
Glacier
Visitor
Center
Biomass
Pre-‐feasibility
Report
Submitted
to
USFS
and
AWEDTG
Greg
Koontz,
PE
Bill
Wall,
PhD
of
Alaska
Wood
Energy
Associates
Juneau
Ranger
District
Office
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 2 | 37 Final Draft
Development Corporation 24 September 2014
Table
of
Contents
1
EXECUTIVE
SUMMARY ......................................................................................................3
1.1
Acknowledgements ................................................................................................................3
1.2
Objective ................................................................................................................................3
1.3
Sources ...................................................................................................................................4
1.4
Scope ......................................................................................................................................4
1.5
Financial
Metrics.....................................................................................................................6
1.6
Resource
Assumptions ............................................................................................................7
1.7
Summary
of
Findings ..............................................................................................................8
1.8
Next
steps ............................................................................................................................18
2
TECHNICAL
SUMMARY ....................................................................................................19
2.1
Existing
Conditions ...............................................................................................................19
2.2
Wood
Fuels
/
Wood
Fired
Heating
Equipment:.....................................................................20
2.3
Proposed
Conditions,
Scenario
1 ...........................................................................................21
2.4
Scenarios
2
through
4 ...........................................................................................................21
2.5
Energy
Savings ......................................................................................................................22
2.5
Cost
Estimate ........................................................................................................................22
Appendix
A.
Interconnections ..............................................................................................23
Interconnections
and
the
Impact
on
Construction
Cost ..................................................................23
Thermal
Storage.............................................................................................................................27
Caveat
Regarding
the
Re-‐use
of
Existing
Boilers .............................................................................27
Appendix
B.
Photos
and
Site
Maps
for
Mendenhall
Glacier
Visitor
Center ............................28
Appendix
C.
Photos
and
Site
Map
for
Ranger
Station
Complex.............................................32
Appendix
D.
Portion
of
Tech
Brochure
for
Pex
Piping ...........................................................36
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 3 | 37 Final Draft
Development Corporation 24 September 2014
1
EXECUTIVE
SUMMARY
1.1
Acknowledgements
This feasibility study was supported by the Alaska Wood Energy Development Task Group and
administered by the Fairbanks Economic Development Corporation. The USFS supported the field study
with information and assistance while in Juneau.
1.2
Objective
The objective of this report is to document the results of a pre-feasibility study performed for the
United States Forest Service (USFS) at two sites in Juneau. Site one contains five buildings (two separate
dorms are treated as one building); the second site consists of only the Mendenhall Glacier Visitor Center
(MGVC). The intent is to document the feasibility of replacing the existing oil and electrical heating
sources with wood in these buildings.
In this report, we distinguish between the evaluation of a district heating plant (DH Plant) and the
evaluation of a building-specific boiler. The analysis methodology is the same for both configurations,
but the data presented for the DH Plant are much more extensive than that in the individual building
analysis.
At the request of the USFS, the study was limited to chip and pellet-fired boilers; no stick fired
boilers were considered. In addition, the USFS has access to three used boilers, which can fire on pellets
or chips. For that reason, we evaluated each “fuel” twice; once with the purchased boiler (Base Case) and
once with a relocated used boiler. The used boilers, manufactured by ACT Bioenergy, were considered to
be free, except for freight and installation costs. Likewise, the USFS has access to three matched thermal
storage tanks; again, these were considered free except for freight and installation.
Feasibility studies are often classified as Level 1 (L1), Level 2 (L2), or Level 3 (L3). Level 1
studies consist of very rough calculations on a small number of important metrics (unit fuel costs, etc) and
can be done remotely. At the other end, L3 studies are commonly called “investment grade studies”; the
level of detail and calculation is so high that one could use the results of an L3 study to get an outside
entity to fund the implementation of the project. Level 2, then, is the bridge between L1 and L3. It is a
Screening study is done to determine if it is worth the time and expense to initiate an L3 study and helps
decision makers determine which aspects, if any, of a proposed project should be included in an L3 study.
An L2 study requires at least a minimum amount of site observation of existing conditions, conversations
with the affected parties, and research with second-order parties (local foresters, vendors, local
contractors, etc). This is a Level 2 study. Level 3 studies are generally quite expensive and thus not
entered into lightly.
Sustainability, Inc (SI) and efour, PLLC (efour) perform L2 and L3 studies across the state of
Alaska, from cities to small villages in the bush. We use the same performance and economic models for
each type of study. For us, the primary difference between the two studies is the quality of the inputs,
which is generally a function of how much time has been spent gathering information and the depth of
that information.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 4 | 37 Final Draft
Development Corporation 24 September 2014
1.3
Sources
The primary sources of information for this study are data collected on site by SI and data
provided by the USFS and the Fairbanks Economic Development Corporation (FEDC). Data collected on
site by SI include existing site conditions, equipment nameplate data, current energy cost data, and
equally important information gathered through discussions with the local stakeholders at the USFS.
In addition to the site knowledge gathered by SI, additional biomass boiler performance and cost
data have been accumulated over the past several years from working with local engineers and
contractors, and from performing multiple L2 and L3 wood-fired feasibility studies.
Hourly weather data for the performance model was extracted from data collected and reported
by the Juneau Airport.
1.4
Scope
The scope of this study is limited to the USFS complex on Mendenhall Loop Road and the
Mendenhall Glacier Visitors Center. The USFS complex consists of three USFS buildings (an office and
two warehouses), two dorms (considered to be one building for this study) and a NOAA office building.
An existing boiler in the USFS office building currently serves the two warehouses with heat via buried
piping. The dorms and the NOAA building are heated with electric heat, so it would be too expensive to
convert the entire buildings to hot water (the output of the biomass boilers).
The NOAA building uses forced air, with electric heating coils on the incoming air, and smaller
coils located throughout the building for terminal (room level) heating control. Rather than try to capture
all the heat by adding hot water coils in each duct that contains an electric coil, we attempted to maximize
the displacement of electric heat while minimizing interconnection costs. We propose therefore to
replace only the large coils that heat the air first. With minimal changes to controls, we believe we can
displace 70 percent of the building heat with hot water in this way.
In the dorms (each two stories, an 8-plex and a 6-plex) the existing heating system consists of
electric baseboard heat. The unit living rooms are the largest spaces, and front on the entry side of the
unit. At each level, there is a covered walkway – new hot water piping could be run in a soffit in the
overhang, and a new hydronic baseboard unit could be piped into each living room. Because the complex
uses more domestic hot water than the NOAA building (which we can displace), we estimate 80 percent
of the dorm heat can be displaced with “wood heat”.
Biomass heating systems are expensive to install. The economics generally work better for larger
buildings, or where two or more smaller buildings can be grouped together and served by a single
biomass boiler, using buried piping between the buildings to distribute the heat. A significant part of the
cost of a district heating plant (DH Plant) is the interconnections to the individual boilers.
The three USFS buildings are already tied together, which significantly helps the economics for
this cluster of buildings. The economics of adding either/both the dorms and/or the NOAA building into
a larger DH Plant, on the other hand, are not favorable. First, they are physically remote from the USFS
building and each other. Second, because they use electric heat coils (in ducts and in baseboard units),
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 5 | 37 Final Draft
Development Corporation 24 September 2014
all the heat cannot be displaced with hot water. Finally, the cost of the interconnections is higher than
simply tying into a building with an existing hot water boiler/piping system.
This report models the performance of one set of (4) DH Plants, and one individual building. In
the model, each configuration of DH Plant is labeled a Scenario; the model shows up to four Scenarios at
a time (they are abbreviated Scenario 1, Scenario 2, and so on). The individual building is the
Mendenhall Glacier Visitor Center, which is on a different site altogether from the rest of the buildings.
For the four DH Plants, we looked at combinations of buildings at the USFS complex; the USFS
building (plus warehouses) was in all four Scenarios. Figure 1.1 shows the makeup of all four Scenarios:
Figure 1.1
The red values are the amount of heat, in kWh, that we believe can be displaced from the
dorms/NOAA, not the total amount of annual heat. For the “non-electric” buildings, the amount of
annual oil use is shown. Scenario 1 is only the USFS 3-building group. Scenario 4 is all five buildings,
and Scenario 2 and Scenario 3 are different combinations between those endpoints.
Due to site factors, 12 analyses were created for each Scenario. These are:
1. Base case, with pellets. This assumes a new pellet boiler
2. ACT case, with pellets. This assumes a relocated, used, ACT boiler is installed
3. Base case, with wood chips. This assumes a new chip boiler
4. ACT case, with wood chips. This assumes a relocated, used, ACT boiler is installed
Four sets of boiler configurations times three pricing alternates = 12 analyses per Scenario
Items 1 through 4 were analyzed first using the current costs for oil and wood products. These
are not favorable to a biomass project because the USFS currently receives oil on a contract at a very low
price of $2.93 per gallon. This low price of oil means there is not much of a unit cost differential between
oil and wood (see Fig 1.2 below). However, when this contract runs out, the USFS may be forced to pay
the same price as the rest of Juneau of $3.85 per gallon. The study therefore looked at the effect of
changes in price in both oil and wood with sensitivity analyses.
The first set of four analyses listed above could be considered the Low Oil / Low Wood case, or
we simply considered it the Base Case. We then looked at four more analyses, with High Oil / Low
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 6 | 37 Final Draft
Development Corporation 24 September 2014
Wood prices. For the final four analyses, we used High Oil / High Wood prices. The results are in
subsection 1.7 below.
1.5
Financial
Metrics
There are a number of financial metrics that can be employed to evaluate a project. Many of
these require that the source and means of financing the project be known. Many require knowing the
expected interest rate that money could be borrowed at, and even the rate of return the client would expect
to achieve if they invested the capital elsewhere (not in the project).
At Level 2, we use two financial metrics. Net simple payback (NSP) does not require any
assumptions about interest rates or escalation rates. It is simply: the project implementation cost divided
by the year one savings, and the units are “years”.
The Benefit / Cost ratio (B/C), on the other hand, requires assumptions on both interest rates and
fuel escalation rates. The B/C is defined below:
The benefit to cost ratio is an attempt to capture the value of the project over the lifetime of the
project; a lifetime of 20 years is commonly used. The output of the calculations included is
actually two numbers, the actual benefit/cost ratio, and the net present value (NPV) benefit of the
project.
The project cost is a one-time event, but the savings accrue over the life of the project.
Depending on the assumed inflation rate of the various fuel sources, the savings may actually
increase each year (if, for instance, oil rises faster than biomass). On the other hand, a dollar
saved in year 20 is not worth a dollar today; it is worth the NPV of one dollar at the assumed
discount rate. The discount rate is the rate of return one assumes the Client could make if that
dollar were invested in some other fashion – in a bank account, or on another project. The
combination of one time and recurring costs, plus inflation and discount means that it would be
very useful if the lifetime benefits, divided by the lifetimes costs, could be boiled down to one
number; the benefit to cost ratio.
The current year is always year zero for the calculation, and it is generally assumed that
construction would be completed in year one (or, for a long process or project, year two). The
NPV of the project cost for a project completed in year one is almost, but not quite the same as
the project cost; it has only been discounted one year. This is the COST part of the ratio. The
BENEFIT is the NPV of the cash stream of savings (fuel savings, in this case) that the project
generates over the 20-year lifetime. Divide the Benefit (in dollars) by the Cost (in dollars), and
you get the dimensionless Benefit to Cost ratio; generally, any value over 1.00 is considered
good, but different agencies have different target values.
The NPV benefit is simply the NPV of the combined (savings minus cost) Cost and Savings cash
flow over 20 years. In the year the project is constructed, the “savings stream” is negative,
because the discounted project cost is much greater than the yearly savings – all other years, the
savings are positive. Take the NPV of that cash stream, and that is the NPV benefit of the project.
Unlike the B/C ratio, this value only really tells one something useful when compared to another
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 7 | 37 Final Draft
Development Corporation 24 September 2014
variant of the same project, or another project that would use the same initial cash input. The
project with the higher NPV benefit (n dollars) is generally better.
The client discount rate and escalation assumptions used in the B/C and NPV Benefit calculations
are shown in Figure 1.2 below. All Building Level and DH Plant summaries indicate the NSP, B/C and
NPV Benefit values for that opportunity. These nominal rates reflect recent escalation rates in SE Alaska.
Note again that while the escalation rates do not affect NSP, they strongly affect the Benefit to Cost
Ratio, which is based on 20 years of energy costs inflated at the rates shown below.
Figure 1.2
At this level of study, it does not matter so much whether these values are correct (as it would in a
Level 3 study) – as long as they are reasonable, and the same for all opportunities; they enable
comparisons of the different configurations and Scenarios.
1.6
Resource
Assumptions
As noted above, the only forms of biomass considered in this report are wood pellets and wood
chips. The oil used by USFS is No. 2 oil.
Figure 1.3 below shows the unit prices and heat contents used for various energy sources in this
report. Note that the units cost values ($/mmBTU) are output heat units; they include the assumed
efficiency of the boiler. Thus, if a gallon of fuel X has 1000 BTU/gal of heat content, using an 80 percent
efficient boiler would mean the same fuel had a heat output of 800 BTU/gal. Electric heat is assumed to
be 100 percent efficient. All heat sources prices are converted to dollars per million BTU ($/mmBTU) so
they can be directly compared. The price as purchased (i.e. in the units in which one buys them) are listed
in the “description” column. The values in the far left column are input heat content, per unit in which the
heat is purchased (per kWh, per gal, etc).
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 8 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.3
As Fig 1.3 shows, at the “Low Oil” price of $2.93 a gallon, the “High Wood” prices are actually
higher per mmBTU. USFS would be losing money to convert to wood in such a price configuration. At
the High Oil price, the Low Wood shows a relatively good price differential of $12.49 (chips) or $10.88
(pellets). In rural Alaska, wood is often $20 to $30 less per mmBTU than oil, thus economy of scale and
low implementation costs are even more important in this case.
1.7
Summary
of
Findings
As noted above, 12 analyses were performed for each Scenario. In order to structure the
information effectively, each Scenario has three tables, and each table has four results. In order, the
results are for: 1) Base Case (pellets), 2) ACT boiler (pellets), 3) Base Case (chips) and 4) ACT boiler
(chips). To re-iterate, the two differences between the Base Case and ACT boiler are: A) in the Base
Case, we assume the project buys a brand new pellet or chip boiler, and B) the actual savings may vary as
the parasitic electric consumption of the boilers vary.
The three tables vary only in the cost of the inputs (thus, the second and third tables constitute a
sensitivity analysis on the price of oil and wood), showing first “Current Oil / Low Wood, then High Oil /
Low Wood, and finally, High Oil / High Wood. Low Oil / High Wood is unworkable for any Scenario,
so, pricing configuration is not presented. In fact, Current (Low) Oil / Low Wood does not work well for
any Scenario and is presented because it is in the current configuration of prices. As long as the oil
prices remain at the current low level, any project would be marginal, at best.
The Tables below each have three footnotes; due to space considerations, these are included here
instead of just below each set of tables:
(1) Implementation cost includes all construction costs, OH&P, and all soft costs (design, etc)
(2) Includes wood pellets, any oil for periods when load exceeds DH Plant capacity, and added
electrical pumping and parasitic energy
(3) Maintenance (chips only) is assumed to be contract labor, and is assumed to be 5 hours a
week, or 1/8th of an FTE – annual FTE cost is assumed to be $60,000/yr, fully burdened
Chip boilers: Viessmann 150 and ACT 1400 | Pellet boilers: (3) x MES 56 and ACT 1400.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 9 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.4 Results for Scenario 1, office building and two warehouses.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 10 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.5 Results for the office building, 2 warehouses and dorms.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 11 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.6 Results for the office building, 2 warehouses and the NOAA building.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 12 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.7 Results for the office, 2 warehouses, dorms, and NOAA building.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 13 | 37 Final Draft
Development Corporation 24 September 2014
To summarize:
• The Base Case values (with new purchased boilers) have much longer paybacks than the
ACT boiler cases (where the USFS relocates a used boiler).
• The Base Cases were presented because they are the “normal” means of implementing a
project, and as such, illustrate the value of having the used ACT boilers available.
• For that reason, it will be assumed that any project implemented will use the ACT boilers; no
further comments will be made about the Base Cases.
• Likewise, none of the Scenarios show strong economics with the current price of oil
(Scenario 1 comes the closest, with a 14.6 year payback on chips) and it is not recommend
proceeding with any of these projects at the current oil price.
• For that reason, all further comments below assume the High Oil price is in effect.
• Due to the increased maintenance associated with the chip-fired boilers, there is only one
chip-fired DH Plant configuration out of the 12 that offers a payback that would be
considered worth pursuing. Scenario 1 (USFS buildings only), with High Oil and Low Wood
prices would be considered. This virtually eliminates a chip-fired DH Plant as an option,
unless USFS assumes the High Oil / Low Wood pricing is very likely to occur.
• Scenario 1 is a relatively strong project on pellets, regardless of High or Low Wood price
(although much better on Low Wood), due to existence of the necessary piping and
interconnections.
• Scenarios 2, 3 and 4 (USFS cluster plus various combinations of NOAA / dorms) are
reasonable projects which might be worth further study, but only in the High Oil / Low
Wood pricing configuration.
• Many of these Scenario results show very favorable benefit to cost ratios (B/C), even when
the simple payback is negative. This is a result of the very high rate of escalation of the Base
fuel, oil, compared to the escalation rate of the alternate, wood. Although the values used are
historically accurate, implementing a project with a negative Year 1 payback, but a very high
NPV and B/C ratio is assuming future commodity prices. AWEA does not recommend such
projects.
Scenario 1 is easily the most viable project of all those analyzed, especially with High Oil / Low
Wood. Figure 1.8 below shows both the monthly fuel values, as well as the costs, for this configuration:
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 14 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.8
In addition to the DH Plants listed above, the MGVC was evaluated for an individual boiler. In
this case, only with wood pellets were considered. The Information package that came from the USFS
noted the importance of maintaining the appearance of the area around the Center. Wood pellets are both
much more energy dense than chips (less storage space required), they are virtually dust-free and often
stored indoors in dedicated bins. The needs of the Center would not be satisfied using wood chips as a
fuel. They are, however, slightly less expensive than pellets on a $/mmBTU basis, so if some means of
maintaining the required level of appearance could be met with stored chips, the economics would be
slightly better.
As with the DH Plants, a Base Case was evaluated utilizing brand new boilers, but none are
economically viable. In all cases, it was assumed the ACT boilers would be used. As above, results, are
shown from top to bottom, with Current (Low) Oil / Low Wood, then High Oil / Low Wood, and finally
High Oil / High Wood. Note that the “22” in the upper right corner of each Table is simply a code which
corresponds to the selected boiler.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 15 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.9
With the Low Oil price, savings are actually negative; the fuel is slightly less expensive, but cost
of the added parasitic electrical load was greater than the small fuel savings. Assuming a High Oil price,
however, the project can be attractive, depending on the price of pellets.
Generally a 20-year cash flow analysis is presented for the Scenarios, however, because of the
number of options, and the fact that most of the numbers would never be used, they are not presented
here. If the USFS indicates an interest in specific Scenarios and price configurations, the report could be
amended with the specific associated cash flows of interest.
The project cost estimates, however, do not change much, one set for pellets, and one for chips,
which are independent of the cost of oil/wood. Figures 1.10 and 1.11 show summaries of these estimates
(these are for the ACT boiler case only, not the Base Case). For pellets:
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 16 | 37 Final Draft
Development Corporation 24 September 2014
Figure 1.10
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 17 | 37 Final Draft
Development Corporation 24 September 2014
For wood chips:
Figure 1.11
All of these potential projects would benefit from higher oil costs and lower wood costs. There is
also a possibility that, as wood pellets and chips become more common in SE Alaska, there will be more
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 18 | 37 Final Draft
Development Corporation 24 September 2014
suppliers and more economy of Scale, causing unit prices to drop rather than rise. USFS must evaluate
the risks of movements in the costs of inputs (oil, electrical energy, chips and pellets).
1.8
Next
steps
From a purely financial point of view, at the current low oil price, the projects may not be very
attractive. If current oil price is projected to remain for some time, the USFS may want to postpone
further work on biomass until the price rises, then re-evaluate.
If, however, that contract will soon expire and may not be offered again, it remains to be
determined what elements are required for a successful project, and the possibility of delivering those
elements within parameters appropriate for the Service.
In addition to financial performance, SI and efour believe that wood energy projects generate
benefits to the Village beyond the obvious monetary ones, called VBECS (value beyond energy cost
savings), a term borrowed from the Rocky Mountain Institute. Among these VBECS are:
• Use of renewable resources
• Reliance on regional, rather than remote energy sources
• Reduced carbon footprint
• Reduced secondary emissions (NOx, S, CO, etc)
• Increased fuel price stability (for future budget planning)
• Energy money spent remains in the regional economy
• Support for developing a stable regional chip or pellet supply
There are, no doubt, others as well. As was noted above, a Level 2 study is a Screening study,
meant to provide enough information to the stakeholders to A) determine how to proceed next, B)
determine whether to proceed, or C) halt the project until conditions improve. This study provides the
information needed to help the USFS and other stakeholders make these decisions.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 19 | 37 Final Draft
Development Corporation 24 September 2014
2
TECHNICAL
SUMMARY
2.1
Existing
Conditions
There are a number of buildings involved in this study, spread across two sites. The existing
conditions at each are summarized in Figure 2.1 below:
Figure 2.1
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 20 | 37 Final Draft
Development Corporation 24 September 2014
As noted above, we believe only about 70 percent of the heating energy can be displaced in the
NOAA building, and 80 percent in the dorms.
2.2
Wood
Fuels
/
Wood
Fired
Heating
Equipment:
Figure 2.2 below shows the properties of the pellets and wood chips that were used in this study
(pellets are assumed to come from the Ketchikan area, and thus have a slightly different composition than
a Juneau chip might have, but the heat content would not be noticeably different):
Figure 2.2
The most pertinent values in Figure 22 are the net useable heat contents, 8,162 BTU/lb and 5,711
BTU/lb, pellets and chips, respectively. Because of their low moisture content (4 percent), pellets are by
far the most energy-dense form of wood fuel, and they generally cost more per BTU.
There are a number of manufacturers of pellet boilers; the basis of design (Base Case) boilers
used in this study are the PES series of boilers made by Maine Energy Systems (MES). There are eight
sizes in the PES series, ranging from 41 kBTU/h to 191 kBTU/h (output).
For the Base Case wood chip systems, the Basis of Design was the Pyrot line of boiler
manufactured by Viessmann of Germany.
The basic pellet system components include:
• A pellet bin, which holds bulk amounts of wood pellets.
o is kept filled by periodic deliveries to the Village by truck and ferry
o allows a number of delivery and loading methods once within the Village
• A means of getting the pellets from the bin into the boiler (material handling)
o a vacuum system; the bin may be up to 66 ft away from the boiler
• The boiler
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 21 | 37 Final Draft
Development Corporation 24 September 2014
o uses onboard controls to modulate the firing rate to meet heating demand
o will remain on and operating as long as the bin is kept filled, and no fuel fouling occurs
o is a “hands-off” unit
• A vent or boiler stack
o vents the products of combustion and boiler emissions into the air through an elevated
stack or vent pipe
o may or may not include additional emissions control equipment
The basic wood chips system components, which differ from pellet system components, include:
• Chip storage, which holds bulk amounts of wood chips.
o a smaller amount is held on site, perhaps one week’s worth, in a covered and (usually)
heated area (a “day bin”)
o usually a larger chip storage area, covered, generally has no side and is not heated
o chips bought by the ton, the large bulk storage is generally at the vendor’s facility, and
not part of the project
• A means of getting the chips from the day bin into the boiler (material handling)
o usually an auger or drag chain
• A means of getting the bulk chips from the vendor into the day bin
o generally owned and supplied by the chip vendor (when buying in bulk)
2.3
Proposed
Conditions,
Scenario
1
In Scenario 1, it was assumed that the new boiler and any chip or pellet storage would be in a
new, dedicated building or container (pre-fabricated boiler plant) between the basement/mechanical room
of the existing USFS office building and the smaller warehouse. The building would be as in Section 2.4.
Since the existing boiler ties into the Warehouses through buried piping, only a single connection is
required to connect all three buildings to a new wood fired boiler.
2.4
Scenarios
2
through
4
In Scenarios 2 through 4, a brand new boiler building is assumed. In the Base Case, this would
be a pre-fabricated containerized Plant, built at the vendor’s facility. Since the assumption is that existing
used boilers are being used, it is also assumed a purpose-built Plant located at the intersection on site
where all four access roads meet.
• The site is leveled, and any fill required is brought in for leveling and freeze protection.
• A new building, about 160 sf, is built on the slab.
• Water, power, sewer and storm drainage are extended to the building.
• The single biomass boiler is installed, and piped up.
• A thermal storage tank is included (see section 3).
• A heat exchanger is installed to separate the primary side (Plant) from the secondary side
(distribution).
• Secondary pumps are installed.
• All required electrical work is installed.
• Automatic controls are installed to control and sequence the boilers.
• PEX piping is run to the USFS Office, NOAA, and the dorms.
• Interconnections are made to each building (Appendix 1).
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 22 | 37 Final Draft
Development Corporation 24 September 2014
2.5
Energy
Savings
As with the cash flows above, too many different tables would be required to represent the
savings for every analysis performed. If the USFS selects exact configurations they might be interested
in, savings summary for those configurations will be provided.
2.5
Cost
Estimate
The construction cost estimate summaries are provided in Section 1 above. Once USFS
determines which, if any, Scenario and fuel is worth further study, a detailed line item estimate for those
Scenarios will be provided.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 23 | 37 Final Draft
Development Corporation 24 September 2014
Appendix
A.
Interconnections
Interconnections
and
the
Impact
on
Construction
Cost
One of the most important features of a District Heating system is the interconnection between
the DH system and the existing buildings systems. These interconnections can range from complex (and
expensive), to very simple, often with one or more variations in between. The simpler the
interconnections, the less expensive they are. However, even the least expensive connections constitute a
significant amount of money. The goal, therefore, is to first minimize the number of connections, and
then apply the lowest appropriate level of technology for each connection, minimizing overall
construction cost.
All possible interconnections should have automated response so that, in the event that the DH
Plant fails, or that the biomass boilers cannot meet the peak loads in very cold weather, operator
intervention is not necessary. At the same time, in periods of the very high heating load, the system
should ideally use 100 percent of the capacity from the biomass boilers first, and use the “back-up” oil
only to cover the peaks.
The following is a summary of some of the things all interconnections should have in common
(Note – these apply when connecting into a building that already uses hot water to distribute heat):
• In all systems, a heat exchanger is preferred between the distribution piping and the building
piping. Many building systems use glycol, while the DH distribution systems use 100
percent water. The heat exchanger provides a physical barrier between the two systems to
prevent cross-contamination, while allowing heat to cross over. A control valve is used on
the distribution return line to control the return water temperature on the building side of the
exchanger.
• Recommended interconnections heat the building hot water return before it gets to the
building boiler(s). The basic premise is that the temperature setpoint for the building return
water coming off the heat exchanger is 5 deg F (for example) hotter than the setpoint of the
boiler itself. If the biomass system heats the building return water to a temperature at or
above the boiler setpoint, the boiler will not come on, HOWEVER,
• If for any reason, the biomass system cannot heat the building return water all the way to
boiler setpoint (failure or very cold weather), the return water temperature will begin to fall,
and when it falls below the boiler setpoint, the boiler will automatically add enough heat to
make its setpoint.
• This ensures that 100 percent of the available biomass heating capacity is utilized before any
back-up fuel is used. Once the load drops to the point where the heat exchanger can heat the
return water to above the boiler setpoint, the building boiler will stop firing.
Given the list above, for any given site, there can be many possible variations in the way buildings are
connected. In general, the size of the DH Plant, the number and nature of the end-users, and the
sophistication of the individual building controls also factor into the decisions on how to interconnect the
buildings.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 24 | 37 Final Draft
Development Corporation 24 September 2014
• For large DH Plants with extensive piping systems, the cost of the pumping energy required
to distribute the heat through the pipes is significant. For that reason, variable speed
secondary hot water pumps are recommended. At any load less than 100 percent, variable
speed pumps cut the pumping energy by 1/4th to 1/8th of the energy of constant volume
system at the same flow. In these situations, the preference is to use a good quality motor-
actuated control valve to control the flow at each building (actually, at each connection – so
there may be more than one per building).
• A motor-actuated valve generally pre-supposes that the building has a pneumatic or DDC
control system to control all of the HVAC systems. Larger, more sophisticated buildings
tend to have such control systems; smaller buildings use only local controls.
• For a DH Plant that serves multiple buildings with multiple owners, a metering system is
installed. This allows the DH Plant to charge the end-users for the exact amount of heat they
use.
Figure1 below shows a typical existing building configuration, with two oil boilers (one for back-
up).
Figure A-1
In a large DH Plant with multiple building owners, one must meter the heat extracted by each
building in order to charge the owner for the heat delivered. Figure A-2 below shows a typical
installation for such a DH Plant. Note however, that Figure A-2 shows a separate HX and meter for each
boiler within the room, that would only be done if each boiler served a separate building tenant. If both
boilers served the building as a whole, then only one set of HXs and meters would be needed.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 25 | 37 Final Draft
Development Corporation 24 September 2014
Figure A-2
Figure A-2 above shows the most expensive means of interconnecting.
The system is configured to heat the building hot water return before it gets to the boiler. The 2-
position valve directly below the pump would be closed, and the other two 2-position valves open;
building hot water return flows to the heat exchanger. The building HWR would be heated, and return to
the boiler loop just above the point it enters the boiler. Because the HWR is now hotter than the setpoint
for the boiler, the boiler never fires. The modulating valves at the HX control the building HWR
temperature, and the flow meters at each HX allow the DH Plant operator to measure the exact amount of
heat consumed by end-user.
For purposes of the USFS, the complexity of Figure A-2 may be inappropriate. An interconnect
that resembles Figure A-3 below is recommended.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 26 | 37 Final Draft
Development Corporation 24 September 2014
Figure A-3
In Figure A-3, all of the actuated valves have been replaced, except that the building HWR
temperature is still controlled by what we have labeled as a self-controlled valve. This valve is controlled
by the expansion and contraction of a fluid within a “sensing bulb” strapped to the pipe and a fluid-filled
line from the bulb to the actuator itself (light dashed line). The hotter the building HWR gets, the more
the fluid expands; the resulting pressure moves the actuator in the valve to modulate and control the HWR
temperature – no external power source or controller is required. The level of precision is not as high, but
is more than enough for the application.
Figures A-1, A-2 and A-3 apply to connecting into an existing hydronic system, which occurs
only at the USFS Office. NOAA and the dorms are heated electrically.
In the NOAA building, much the same principle of control is used. New HW coils would be
installed upstream of the electric coils, in the main air handling equipment. The HW coils would have a
higher setpoint than the electric coils, so that if the HW coils hit their setpoints, the electric coils never
come on. If the HW system fails for any reason, the electric coils will simply work exactly as they do
now.
In the dorms, installation of new hydronic (HW) baseboard heating is recommended in the living
spaces of each of the 14 units. Ideally, the electric baseboard units would be left in place as back up (and
controlled exactly as the electric coils would be at NOAA). This would have to be determined in further
Level 3 studies of this site.
The added expense of the HW / electrical connections, plus the fact that all of the electric heat
cannot be displaced in either building, the economics of Scenarios 2, 3, and 4 are much less attractive
than those of Scenario 1.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 27 | 37 Final Draft
Development Corporation 24 September 2014
Thermal
Storage
The used ACT boilers available are all actually larger than the application requires. This
normally means the boilers will cycle on and off significantly more than a boiler that is well matched to
heating demand. Thermal storage provides a number of benefits, and has been included in these proposed
projects. This subsection reviews the utility and benefits of thermal storage.
When referring to a hot water heating system, thermal storage simply refers to a hot water tank,
which stores hot water (thermal storage). The importance of using thermal storage in a biomass-fired
heating plant varies depending on the form of the wood and type/size of the boiler.
Stick fired boilers are batch fed, with an operator adding batches of fuel as needed. In this case,
thermal storage is a requirement, because once the fuel starts burning, it is impossible to modulate the rate
of burn to match the heat load. Instead, the amount of fuel added is sized to heat the thermal storage,
while the pumping/piping system extracts heat from the thermal storage as needed to match the load. The
thermal storage “de-couples” the rate of burn from the variations in heating load.
Chip fired boilers are automatically fed, and can modulate to meet load. It would seem then that
they would not need thermal storage, and in fact many chip systems are installed without storage. Where
storage really provides value in a chip system is when the heating load varies over a very large range, as
they do in Alaska, or when the boiler is significantly oversized, as at the USFS. The boiler can only turn
down to about 25 percent of full load capacity; below that heating demand, the boiler will cycle off until
hot water temperature drops a set amount, and then restart. A good chip boiler will auto-restart, but they
still will not cycle On and Off like an oil boiler, for instance. Once the fuel is in a solid fuel burner, it will
burn whether the heat is needed or not. They take a long time to cool down, and an equally long time to
heat back up. Finally, if the fuel is very wet, the auto-start may take a long time, or in extreme cases, fail.
A thermal storage tank helps limit the cycling, the boiler now modulates to keep the tank at setpoint, and
as above, the system extracts heat from the tank as needed. The thermal storage can keep the boiler
running at very low levels rather than cycling.
The performance of pellet boilers is as close to an oil-fired boiler as is possible with wood. The
fuel is very dry, and easy to re-start. The boilers are generally much smaller than chip boilers, so there is
not much fuel in the unit at any given time. They are not as heavy, so they heat up much quicker. While
a thermal storage tank would again limit cycling at low loads, pellet boilers do not strictly require a tank
to modulate and follow loads (although, as noted above, AWEA prefers to utilize them, and the
performance as modeled (and priced) does include thermal storage). However, all good pellet boilers
have an auto-cleaning feature, where they clean the tubes, generally once a day. Many models cannot do
this while the boiler is actually running, so they shut down. Such boilers generally use thermal storage to
“bridge over” the time they are off.
Caveat
Regarding
the
Re-use
of
Existing
Boilers
NOTE THAT SI AND EFOUR have never seen the used ACT Bioenergy boilers and associated
thermal storage tanks that are being proposed for this project. We have assumed, for convenience, that
they have the stated capacities we were supplied with, that they are in good working order, and that they
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 28 | 37 Final Draft
Development Corporation 24 September 2014
can operate efficiently with pellets or chips. SI and efour provide no assurances, nor do we warrant that
these assumptions are valid.
Appendix
B.
Photos
and
Site
Maps
for
Mendenhall
Glacier
Visitor
Center
The Mendenhall Glacier Visitor Center is a special site in that the foundation is placed on bed rock and
there is an interest in keeping the site as natural looking as possible. There is not space in the boiler room
for a pellet boiler and external installation is unacceptable. The site below is a shop built into the rock
with a wooden roof, which can be removed for installation of a boiler. Note that the roof is an
observation deck for the glacier. (Figure B-1)
Figure B-1. Mendenhall workshop location for a pellet boiler
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 29 | 37 Final Draft
Development Corporation 24 September 2014
Figure
B-2. Mendenhall entrance where pipe will enter the building and then up a chase to boiler room.
There is an utilidor under the walkway.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 30 | 37 Final Draft
Development Corporation 24 September 2014
Figure B-3. Boiler room in the interior of the visitor center building.
Figure B-4. Boiler Label.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 31 | 37 Final Draft
Development Corporation 24 September 2014
Figure B-5. Site map for Visitor Center showing shop location, access for pellet delivery to an inside bin
with a shoot leading into it and distance from building.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 32 | 37 Final Draft
Development Corporation 24 September 2014
Appendix
C.
Photos
and
Site
Map
for
Ranger
Station
Complex
The ranger station complex is made up of three buildings connected together as on heating system with
one boiler that heats all located in the office building. The other two buildings are two warehouses. On
site there are three other buildings, two dorms considered one building in the analysis and a NOAA
building. Both are heated with electricity.
Figure C-1. USFS Ranger Station boiler room. This boiler heats three buildings.
Figure C-2. Boiler Label
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 33 | 37 Final Draft
Development Corporation 24 September 2014
Figure C-3. Domestic Hot Water System
Figure C-4. Ranger Station Office Building
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 34 | 37 Final Draft
Development Corporation 24 September 2014
Figure C-5. Two warehouse shop buildings heated from office building.
Figure C-6. NOAA office building heated with electricity.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 35 | 37 Final Draft
Development Corporation 24 September 2014
Figure C-7. Two dorms heated with electricity.
Figure C-8. Site map for USFS Ranger District Complex.
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 36 | 37 Final Draft
Development Corporation 24 September 2014
Appendix
D.
Portion
of
Tech
Brochure
for
Pex
Piping
PRE-FEASIBILITY STUDY on WOOD-FIRED HEATING PROJECTS Sustainability, Inc
USFS | Juneau, Alaska efour, PLLC
For Fairbanks Economic 37 | 37 Final Draft
Development Corporation 24 September 2014